Orchestration · Software component
Phase Barrier Executor
Software componentOrchestrationOrchestration & Toolsarc:PhaseBarrierExecutor
A dependency-ordered executor that runs topologically sorted phases in sequence, executing agents within a phase in parallel and blocking at a barrier until all have completed before starting the next phase.
Responsibility. Executes workflow phases in order with synchronisation barriers between them.
Also known as: Synchronous phase barriers, Execution barriers
Variant of Dependency-Ordered Executor abstract
When to choose. Choose when simple, robust failure semantics matter more than maximal parallelism: a failure in a phase stops the workflow immediately, at the cost of waiting for the slowest agent of each phase.
Relationships
alternative to variability
Design guidance
- SHOULD additionally verify each agent's declared dependencies have completed before it starts, as defense-in-depth against phase-ordering bugs.
- SHOULD monitor per-phase latency to detect single-agent phases that dominate workflow latency and consider splitting their work.
Quantitative guidance
As stated by the sources; verify before use.
- Out-of-order execution fell from 40% of failures to 0% after phase barriers (Ch8.2A).
- Phase imbalance: Phase 0 2.1 s, Phase 1 (Analyst alone) 4.8 s, Phase 2 1.9 s average (Ch8.2A).
Classification
- Patterns
- Barrier synchronizationPhase-based executionDefense-in-depth dependency check
- Quality attributes
- Reliability (ISO/IEC 25010 | NIST AI RMF: valid and reliable)Maintainability (ISO/IEC 25010)
- Risks mitigated
- Out-of-order executionCascading failures of dependents
Sources
- Ch8.2A: T. Nguyen, "Error Rates and Reliability," in Mastering Agentic AI Systems: Guide for the NVIDIA NCP-AAI Exam, 1st ed. 2026, ch. 8.2A. ISBN: 9798244538229.